Anarchy is fixed (usually a turn, but depending on number of civics you change at a time) and not proportional to game speed AFAIK. It means that Spiritual is almost worthless on Marathon and very potent on Quick.
Spiritual makes it "possible" to switch 1 civic at a time on quick (where it's usually wasteful to not switch 2 or 3 at once), and multiple civics at once on Marathon (where normally it would be like 8 turns of anarchy). So it functions differently, but on sum it's pretty much equally useful regardless of game speed.
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